Chair back



FIG. 1 is a top view of a chair back showing my new design with astraight edge across from the curved top and lower point;

FIG. 2 is a left view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a right view thereof;

FIG. 5 is a bottom view thereof;

FIG. 6 is a back view thereof; and,

FIG. 7 is a perspective view thereof.

CLAIM The ornamental design for a chair back, as shown and described.